Patent GB-795399-A (GB)
Title: Improvements concerning hydraulic amplifier devices and systems
IPC: B64C13/00
Filed: 1955-12-22
Abstract: 795,399. Fluid-pressure servomotor control systems. GENERAL ELECTRIC CO. Dec. 22, 1955 [Dec. 30, 1954; Dec. 30, 1954], No. 36727/55. Class 135. An hydraulic system comprises a valve piston 28, Fig. 1, movable in response to pressures in control chambers 13, 14 at each end thereof through which pressurized fluid is continuously supplied and passed through to a sump, independent pressure control means 11, 12 for each chamber, and pressure control means through which the pressure fluid is supplied to each chamber and the effect of which is varied by movement of the valve piston. As applied to a steering control surface 16 of a dirigible craft the valve piston 28 controls a servo piston 38 and the pressure controller 11 consists of a valve 49 actuated by a solenoid 18 under the control of a manually operated member 17 or an automatic pilot. The pressure control means 12 consists of a similar valve 44 linked to the control surface 16. Pressure fluid is supplied at 22 and passes through ports 23, 24 and annular restrictions 25, 26 to the chambers 13, 14 from which it escapes through passages 48, 45 and annular restrictions surrounding portions 50, 46 of the valves 49, 44 to exhaust ports 51, 47. Movement of the valve 49 causes a change in the resistance to fluid escaping through the exhaust port 51 thereby altering the pressure in the chamber 13 and causing movement of the valve piston 28 to admit pressure fluid to one side of the servo piston 38 and connect the other side to an exhaust port 34. The movement of the valve piston also causes a change in the resistances offered by the restrictions 25, 26 to arrest movement of the valve piston. The movement of the control surface 16 is transmitted to the valve 44 to alter the resistance presented to fluid escaping from the chamber 14 so that ultimately the valve piston 28 is recentred after the servo piston has moved an amount corresponding to the displacement of the member 17. In a modification, the servo piston is anchored to a fixed member and the servo cylinder 28 together with the housing for the valve piston 28 is connected to the control surface 16 so that " follow-up " is obtained without the connection from the control surface to the valve 44. The valve 44 is then connected through a solenoid to an attitude stabilization damper consisting of a rate gyro and an electrical amplifier so as to impose a further control on the valve piston 28. In this modification the valve 49 is actuated directly by a manually operated lever instead of through the solenoid 18. In a further modification, the servo piston actuates a valve controlling the motive fluid supply to an engine for controlling the speed thereof and the pressure in the chamber 14 is governed by a pump driven by the engine, the valve 49 being manually operated to select the engine speed. Alternatively the pressure in the chamber 13 may be governed by another pump so that the speed of the controlled engine may follow that of another machine. In a further modification, the servo piston 38 actuates a valve 69, Fig. 4, controlling the motive fluid supplied to an engine 64 and the latter drives an eccentric 66 which reciprocates a rod 67 connected through springs 60, 61 to masses 62, 63 connected to the valves 44b, 49b. The spring- mass assemblies 60, 62 and 61, 63 are arranged to have natural frequencies of vibration above and below the frequency at which the engine 64 is to be controlled. The position of the valve piston 28 may be indicated visually by a pointer. In a further modification, the two valves 44b, 49b, which are single rather than double landed, are oscillated electromagnetically by a winding energized by the output from an A.C. generator or a D.C. generator with a pronounced " ripple " and the valve piston 28 controls a variable speed hydraulic coupling in the drive between a power plant and the generator. When more than one generator is connected in parallel a further winding operative on the valve 44b only may be provided to equalize the loads on the generators.